ok. I see. But most assemblers do use "$" to represent the location of the current instruction right?
At least ASEM-51 does.

As for newbies, I would suggest

AJMP $
END

as the last two lines of code.

or if you have routines, I suggest you add:

AJMP $

before the start of a routine (whose names normally appear after LCALL and/or ACALL)

For example, this code:

---- your mainline code here
AJMP $

routine1:
---- your routine1 code here
RET

routine2:
---- your routine2 code here
RET

AJMP $
END


is better than this code:

---- your mainline code here

routine1:
---- your routine1 code here
RET

routine2:
---- your routine2 code here
RET

END

Because the second code will run the 1st routine after the mainline ends whether or not the routine has been called. Also because of RET, it will run code at address R6:R7 (or is it R7:R6?) immediately after RET is executed, provided register bank 0 is used (which is the default setting), and SP remains at 07h.